The dc block charge diagram of an ideal MOS capacitor is shown. (a) Is the semiconductor substrate n-type or p-type? Explain. (b) Is the device in accumulation, depletion, or inversion? (c) Draw the energy band diagram corresponding to the charge state pictured in the block charge diagram.
![Q. 4 The capacitance-voltage (C−V) characteristic of a silicon MOS capacitor is shown in Figure Q4. The capacitor comprises a metal gate with a work function of 5.62 eV. The gate dielectric is made of silicon-dioxide (SiO2) with a relative permittivity of 3.9. (a) Sketch the block charge diagram corresponding to point (1) on the C - V curve. [4 marks] (b) If the capacitor area is 2×10−3 cm2, determine the oxide thickness. [3 marks] (c) Determine the depletion layer width at point (2). [4 marks] (d) Briefly describe two ways to reduce the threshold voltage of the capacitor. [4 marks] (e) If the flatband voltage is 0.7 V, determine the work function of the substrate. [3 marks] (f) Sketch the energy band diagram corresponding to point (2) on the C - V curve. Is the capacitor under accumulation, depletion, or inversion? Briefly explain. [7 marks] Figure Q4: Capacitance-voltage (C−V) characteristic of a silicon MOS capacitor.](https://www.doubtrix.com/uploads/editor/3301654154bUocnyQJRA.png)
